An ophthalmic device or a method of operating such a device allows performing one or more procedures with respect to an eye of a patient, i.e., an ophthalmic application, such as a surgical, therapeutic or diagnostic procedure, e.g., including and not limited to, LASIK (Laser-Assisted in-situ Keratomileusis), Epi-LASIK, PRK, lenticule extraction or keratoplasty.
A fixation of the eye during the ophthalmic application, e.g., a laser ablation, can be avoided by tracking eye movement, e.g., involuntary saccades, in real-time. In this case, the application field includes an ablation profile that is applied to the cornea according to the application field. The application field of the laser ablation is laterally repositioned relative to the ablation laser so that the application field remains centered at a predefined centering point on the cornea.
For controlling the ablation laser, a camera observes the pupil center of the eye as a point of reference used for centering the application field. Existing systems for refractive surgery center the application field to the current pupil center, optionally in combination with one or more further corneal points. Such further corneal points can be topographically defined depending on the ametropia of the eye (e.g., myopia, hyperopia or astigmatism). Since the pupil center may shift relative to the cornea when the iris of the eye astringes or dilates, the pupil center shift is compensated, as described in document EP 1 985 269 A1.
Some known systems allow manually offsetting the centering point away from the pupil center. The offset can be important, if the pupil center of the eye highly deviates from an optical center of the eye or a topographic center of the corneal surface. However, manually offsetting the centering point is conventionally based on a subjective visual estimate and limited by instruments used for visual inspection, e.g., a microscope resolution. In addition, the mere fact that the offset is performed manually can introduce a factor of uncertainty and contribute to an inaccuracy of the ablation result, e.g., after application of medication and use of surgical instruments. Furthermore, the manual offset is time-consuming and requires additional effort by the surgeon.